Apparatus for agitating and aerating liquids or pulps.



A. G. HOWARD.- ATING AND AERATING LIQUIDS OR PULPS.

IIIIIIIIIIIIIIIII 0V.19,1912.

Patented Jan. 13, 1914.

A. G. HOWARD.

APPARATUS FOR AGITATING AND AERATING LIQUIDS 0R PULPS.

IIIIIIIIIIIIIIIIIIIIIIIIII 2.

1,084,21 O. Patented Jan. 13, 1914.

4 EEEEEEEEEEEE 3.

A. C. HOWARD.

APPARATUS FOR AGITATING AND AERATING LIQUIDS OR, PULPS.

APPLICATION FILED NOV. 19, 1912.

1,084,210,, Patented Jan. 13, 1914. I

4 SHEETS-SHEET 4.

UNITED STATES PATENT OFFICE.

ALLEN CRAWFORD HOWARD, OF LONDON, ENGLAND, ASSIGNOR TO MINERALSSEPARATION LIMITED, OF LONDON, ENGLAND.

, APPARATUS FOR AGITATING AND AERATING LIQUIDS 0R PULZPS.

Specification of Letters Patent.

Patented Jan. 13, 1914.

Application filed November 19, 1912. Serial No. 732,286.

To all whom it may concern:

Be it known that I, ALLEN CRAWFORD HOWARD, a subject of the King ofEngland, residing at London, England, have invented certain new anduseful Improvements in Apparatus for Agitating and Aerating Liquids orPulps, of which the following is a specification.

This invention is for improvements in or relating to apparatus foragitating and aerating liquids or pulps. In this specification the termagitating is used to include such operations as disseminating uniformly.and efliciently through a bulk of liquid any other substance, gaseous,liquid or powdered solid in any proportions. It also includes suchturbulent mixing as is necessary where difi'erent materials have to bebrought into intimate contact with one another. The term aerating isused to include the introduction of any gas into a liquid, whether thegas be soluble or not, and the dissemination of the gas in a state offine division in the liquid. It also includes the emulsification of agas in a liquid and in this specification particularly signifies theintroduction into a liquid of the supernatant gas such as air. Theexpression liquid is used to'include pure liquids such as water, orsolutions, or mixtures of liquids, or mixtures of liquids and powderedsolids such as mineral pulps.

The invention has arisen in connection with the well-known agitationfroth process for concentrating ores by flotation as described forexample in the United States Patents Nos. 835120 and 962678, butapparatus embodying the invention can be utilized in any otherindustrial process in which agitation and aeration are involved.

An apparatus for agitating and aerating liquids or pulps according tothis invention comprises the combination with a vessel having flat sidesor more or less vertical baffles and an agitator rotated about avertical axis and comprising a number of vertical blades (substantiallyradial) curved horizontally and a circular horizontal plate beneath theblades or intercepting them, the agitator being preferably rotated withthe concave side of the blades foremost whereby the liquid between theblades is ejected horizontally with such force and produces such adegree of convection that the gas above the liquid is effectively drawninto the liquid and disseminated throughout it in a finely dividedstate. In the agitator employed, it is preferable according to thisinvention that the curved radial blades do not extend inward to theaxis, either above or below the horizontal plate or both.

According to a further feature of this invention the apparatus foragitating and aerating liquids or pulps comprises the combination with acentrifugal agitator of a multiplicity of more or less vertical bafilesconsisting of expanded metal, lattice work, grid or grating, so placedthat flat faces thereof intercept or obstruct the rotary move ment ofthe liquid, the bailles being disposed around .the agitator or extendingupward to a greater or less extent. These bullies are preferably incontact with the walls of the containing vessel and constitute reentrantangles.

In the agitation-froth process of concentrating ores referred to aboveit is at present the practice to agitate and aerate the pulp mixture inone vessel and thereafter to run it out into another vessel such as aspitzkasten where (owing to the comparatively quiescent state of theliquid) the froth forms ing a powerful convection within the pulpwithout subjecting the whole surface of the pulp to turbulence wherebythe pulp may be efficiently agitated and aerated, while at the same timea portion of the surface of the pulp is sufiiciently quiescent to allowof the formation and removal of mineralbearing froth.

In the accompanying drawings which illustrate by way of example forms ofapparatus embodying this invention and designed to carry out theagitation froth process of concentrating ores, Figure 1 is a perspectiveview of a single unit of the agitating apparatus only with one wallpartly broken away. Fig. 2 is a perspective view in tive view of amodified form of the appabroken away. Fig. 5 is a ratus partly brokenaway, the outer vessel being shown of glass to render the internalconstruction visible. Fig. 4' is a perspective view of a modified formof apparatus partly erspective view in section of a modified/ mm of theapparatus.

Referring to Fig. 1 the agitation and aeration vessel consists of arectangular box A conveniently of wood with an inlet B and an outlet Csuitably arranged. It is adapted to be used with one or morespitzkastens as in the construction shown in the patent to Hebbard, No.1,064,209, or the patents to Hoover, Nos- 953,746 and 979,857. Theagitation and aeration vessel is provided with an agitator rotated by avertical spindle D the agitator being immersed in the liquid. Theagitator itself comprises a flat horizontal plate E mounted on thespindle D. Above this plate are a number of (say eight) substantiallyradial vertical blades F horizontally curved. These blades may beprovided also beneath the horizontal plate as at .F. The blades areshort arcs. They do not extend inward to the spindle D. The function ofthe blades is to throw the liquid between them violently outward in ahorizontal direction thus creating a very powerful convection combinedof course with rotary motlon.

Referring to Fig. 3, the outer vessel A- and the agitator D, E. F, F maybe constructed,

and arranged as above described. Within the vessel A surrounding theagitator, and preferably in contact with the walls of the vessel, isplaced a strip of expanded metal or lattice work G so placed that flatfacesthereof intercept or obstruct the rotary movement of the liquid.This expanded metal or the like G may be furnished only in a beltsurrounding the agitator E, F, F, or it may extend upward and downwardas much as is necessary to give the most eflicient result.

Referring to Fig. 4, the vessel A, and agitator D, E, F, F may beconstructed and arranged as above described. Within the vessel A andpreferably close to the walls of the vessel is arranged a grid orgrating H so placed that flat faces thereof intercept or obstruct therotary movement of the liquid. 7.

When the agitator is rotated .it is found that the liquid between theblades is thrown out horizontally with such force as to create a verypowerful convection combined with rotary motion around the verticalaxis. Whenever the streams of liquid are obstructed as by a fiat side ofthe vessel or by a battle therein, eddies are set up, introducing intothe liquid bubbles of air, which are immediately sucked downward by theconvection action, thrown violently out by the centrifugal action and toa greater or less extent drawn around by the rotary motion of theliquid. Ti herever streams of bubbles meet obstructions such asflatsides of the vessel or more or less vertical baiiles they are brokenup and tend to be emulsified in the water. One function of thehorizontal plate E is to intercept the downflowing water, to retain itwithin the sphere of action of the blades F and thus'to increase thepositive action of said blades. The blades F below the horizontal plateact to throw out the pulp below the plate E thereby preventingquiescence there and promoting the total centrifugal or pumping effectof the agitator.

Referring to Fig. 5 the agitator D, E, F, F is constructed as before androtates in the center of an outer vessel J which is enlarged at the topin the form of an inverted cone J surrounded by a launder J Between theouter vessel J and the agitator is placed a grating H which is open nearthe bottom thus forming orifices H. The upper part of the grating iscovered by a plate K which extends above the top of the outer vessel JJ. The ore pulp is'fed into the center of the apparatus through aconduit L and the frothing agent or agents are also fed into the centerof the apparatus. When the agitator is rotated a violent agitation andaeration is set up within the grating K, but outside the grating thesurface of the liquid in the outer vessel J J is practically still sothat the aerated pulp is ejected through the orifices H in the gratingand the froth forms at the water surface between the grating and theouter vessel, and the froth overflows in the launder J If the liquid(such as an ore pulp) contains an air emulsifying agent (such aseucalyptus oil) it is found that the air is emulsified in the liquidwith extraordinary rapidity and'eiiiciency so thatv this inventionaffords an economy in the agents necessary in processes such as theagitation-froth process. The agitation and aeration produced byapparatus according to this invention is found to be so peculiarlysuitable and efficient in the treatment of the ore pulpby processes suchas, for example the agitation froth process, that it not only readilyadmits of a large increase in the percentage of solids which may bepresent in pulp to be treated, thereby increasing the quantity of orethat can be treated in a given plant and in a given time; but it alsopermits a much more dilute pulp to be successfully treated for therecovery of values-such as for example from a Very fine ore slimecarrying metal values suspended in a large quantity of 1iquidespeciallywhere settlement or thickening of such dilute pulp is diflicult toeffect.

The eflicienoy of the agitation and aeration produced by this apparatusis so great as to enable great reduction in the power consumption of theagitation and aeration devices employed in the agitation-froth processof ore concentration for example.

The method of constructing the apparatus may be varied without departingfrom this invention as for example the blades of the agitator may bevaried in shape and in curvature. Thus, they may be made thicker atthose places where wear is likely to take place.

What I claim as my invention and desire to secure by Letters Patentis 1. In an apparatus for agitating and aerating liquids or pulps, thecombination with a vessel having internal vertical faces, of a rotatingagitator arranged to rotate about a vertical axis in the vessel andcomprising a number of substantially radial vertical blades curvedhorizontally and a circular horizontal plate transverse to the blades,whereby the llquid between the blades is ejected horizontally with suchforce and produces such a degree of convection that the gas above theliquid is efiectively drawn into the liquid" and disseminated through itin a finely divided state.

2. In an apparatus for agitating and aerating liquids or pulps, thecombination with a vessel having internal verticalfaces, of a rotatingagitator arranged to rotate about a vertical axis in the vessel andcomprising a number of substantially radial vertical blades which arecurved horizontally but which do not extend inward to the axis and acircular horizontal late transverse to the blades, whereby the llquidbetween the blades is ejected horizontally with such force and producessuch a degree of convection that the gas above the liquid is eflectivelydrawn into the liquid and disseminated through it in a finely dividedstate.

3. In an apparatus for agitating and aerating liquids or pulps, thecombination with an outer containing vessel having flat sides, of arotating agitator arranged to r0- tate about a vertical axis in thevessel and comprising a number of substantially radial vertical bladescurved horizontally and a circular horizontal plate transverse to theblades, whereby the liquid between the blades is ejected horizontallywith such force and produces such a degree of convection that the gasabove the liquid is effectively drawn into the liquid and disseminatedthrough it in a finely divided state.

4:- In an apparatus for agitating and aerating liquids or pulps, thecombination of a containing vessel, a centrifugal agitator thereinrotatable about a vertical axis and comprising a number of substantiallyradial vertlcal blades curved horizontally and a circular horizontalplate transverse to the blades, and a number of substantially verticalbaflies so fixed in the vessel that the flat faces thereof intercept orobstruct the rotary movement of the liquid.

5. In an apparatus for agitating and aerating liquids or pulps, thecombination of a vessel, a centrifugal agitator rotatable about avertical axis therein and comprising a number of substantially radialvertical blades curved horizontally and a circular horizontal platetransverse to the blades, and a grating within the vessel arranged tointercept or obstruct the rotary movement of the liquid, the vesselhaving an outlet opening across which the bars of the grating extend.

6. In an apparatus for agitating and aerating liquids or pulps, thecombination of a' vessel, a centrifugal agitator rotatable therein, anda grating within the vessel arranged to intercept or obstruct the rotarymovement of the liquid, the vessel having an outlet opening across whichthe bars of the grating extend.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

'ALLEN CRAWFORD HOWARD.

Witnesses.

WILLIAM H. BgiLLAN'rYNE, PHILLIPS CRAWLEY.

